Molding method

ABSTRACT

This application relates to a molding method including steps of embedding a form made of an instantaneously combustible material in a filler material in a flask covering the top of the flask, inducing negative or sub-atmospheric pressure in the filler material thereby compacting same, and pouring a molten metal into the form, whereupon the form material is gassified and the resultant gases are positively removed from the mold system.

Unlted States Patent 1191 1111 3,861,447 Hondo Jan. 21, 1975 [5 MOLDINGMETHOD 3293,7133 12/1966 Taccone 164/160 3,339,6 0 9 1967 Krz a 0 s iet164/34 X [751 lnventoTsI M3530 Susaka, Japan 3,410,942 11/1968 1311;61:617. 164/34 ux [73] Assignee: Kabushiki Kaisha Akita, Susaka ,3602/1969 Olson 164/195 X i Japan 3,520,349 7/1970 Watts 164/34X 3,557,8671/1971 Krzyzanowski... 164/34 X [22] Filed: Oct. 27, 1972 3,572,4213/1971 Mezey et a1. 164/34 X App O 503 3,581,802 6/1971 Krzyzanowski164/34 Primary ExaminerAndrew R. Juhasz [30] Foreign ApplicationPriority Data Assistant ExaminerV. K. Rising Dec. 14, 1971 Japan46-101264 At y, g nt, or i mt e s, Da is, Miller &

Dec. 25, 1971 Japan 46-1813 Mosher July 3, 1972 Japan 47-66787 July 13.I972 Japan 47-70233 57 ABSTRACT This application relates to a moldingmethod including [52] U.S. Cl 164/34, 164/160, 164l/(1Z/07, Steps ofembedding a form made of an instantaneously [51] Int Cl Bzzc 9/02combustible material in a filler material in aflask cov- [58] Fie'ld Us195 ering the top of the flask, inducing negative or subl64/l96, 2467197 7 169 170, 171, 160 atmosphenc pressure 1n the filler matenalthereby compacting same, and pouring a molten metal into the form,whereupon the form material is gassified and the [56] References .Cltedresultant gases are positively removed from the mold UNITED STATESPATENTS system. 2,652,609 9/1953 Sudia, Jr. 164/7 3,259,949 7/1966 M0016164/34 4 Claims, 6 Drawmg Flgllres ll IO PATENTED JANE] I975 sum 3 or 3MOLDING METHOD This invention relates to a molding method.

In one molding method known in the art as a full mold method whichpermits simplification of a molding operation, an instantaneouslycombustible form made of a bubble producing synthetic resinous materialis embedded in a filler material in a flask, and a molten metal ispoured into the form to produce a casting.

Some disadvantages are associated with this molding method. Gasesproduced, when the form is burned by the heat of the molten metal or theshrinkage of the form caused by the heat of the molten metal may destroythe shaping surfaces of the form and render them irregular. As a result,the filler material may get entangled in the molten metal, causingfusion and penetration to occur in surfaces of the casting produced.

Moreover, gases produced when the form is burned by the heat of themolten metal may stay in the mold and their pressure may cause themolten metal to flow in reverse current to the gate. This makes itimpossible to perform pouring satisfactorily, thereby preventing aproduct of good quality from being produced.

This invention has as one of its objects the provision of a moldingmethod which obviates-the aforementioned disadvantages of the prior art.

Another object of the invention is to provide a molding method in whichan instantaneously combustible form is embedded in a filler material toform the filler material into a shape which is in conformity with theshaping surface of the form and a molten metal is poured into the formafter a negative or subatmospheric pressure is induced in the fillermaterial to maintain the shape 'of the filler material. Part or thewhole of the gases produced when the form is burned by the heat of themolten metal is drawn into the tiller material to reduce the influenceof gases on the product. The filler material is rendered compact andmaintained in the desired shape by the negative pressure. Thus, thefiller material need not contain a binder therein, thereby facilitatingremoval of the filler material fr'om the product after being taken outof the mold and making it unnecessary to effect adjustments of thecomposition of the filler material. This molding method enablesincreases in operational efficiency, with the filler material being usedagain and again.

Another object of the invention is to provide a molding method in whichan instantaneously combustible form-is covered with a shield memberbefore being embedded in a filler material to form the tiller materialinto a shape which is in conformity with the shaping surface of theform, and a molten metal is poured into the form after a negative orsubatmospheric pressure is induced in the filler material to render thetiller material compact and have the shape of the filler materialmaintained. The presence of the shield member between the fillermaterial and the molten metal precludes disintegration of the fillermaterial, entanglement of the filler material in the molten metal tocause fusion and penetration to occur on the surfaces of the castingproduced. This molding method enables a casting of a predetermined shapeand high quality to be produced positively.

Another object of the invention is to provide a molding method in whicha gas vent is provided on an instantaneously combustible form embeddedin a filler material to form the filler material into a shape which isin conformity with the shaping surface of the form, and a molten metalis poured into the form. By this arrangement, gases produced when theinstantaneously combustible form is burned by the heat of the moltenmetal can be readily vented to atmosphere as soon as they are producedwithout remaining in the mold and the molten metal can be poured intothe form without any trouble, so that a casting of a predetermined shapeand high quality can be produced positively.

Other and additional objects as well as features and advantages of theinvention will become evident from the description set forth hereinafterwhen considered in conjunction with the accompanying drawings, in which:

FIG. 1, FIG. 2 and FIG. 3 are vertical sectional views of the mold usedin the different embodiments of the molding method according to thisinvention;

FIG. 4 is a flask used in another embodiment of the molding methodaccording to this invention; and

FIG. 5 and FIG. 6 are vertical sectional views showing molding steps ofthe molding method according to this invention.

A first embodiment of the invention will be described with reference toFIG. I in which 1 designates a flask having an open top and providedwith an evacuation pipe system 2 formed therein with a multitude ofopenings 3 and having a filter 4 made as of wire netting wound thereon.The evacuation pipe system 2 is formed at one end thereof with anevacuation port 5.

6 is a form made of an instantaneously combustible synthetic resinousmaterial, such for example as foamed polystyrene, and having a shapesimilar to the shape of a casting to be produced. As shown, the form 6comprises a main body 7 of a polygonal annular shape defining an opening8 and having a plurality'of openings 9 in the body, a runner l0 and agate 11, the runner 10 andgate 11 being also made of an instantaneouslycombustible synthetic resinous material and formed integrally with themain body 7.

In operation, the form 6 is placed in the flask l and a filler material12 which'may be molding sand or other heat resisting particlematerialfills the flask so that the filler material 12 may fill theopenings 8 and 9. The flask l and the form 6 are vibrated as a unit bymeans of a vibrator (not shown) to solidly pack the filler material.

Then, the open top of the flask l is covered with a lid 13 which may beof a synthetic resin film, and the interior of the flask l is evacuatedby a vacuum pump (not shown) or any other suction means which isconnected to the evacuation port 5 of the evacuation pipe system 2 so asto induce a negative or sub-atmospheric pressure in the flask. A moltenmetal is poured through the gate 11 and the runner 10 into the main body7 of the form 6. The form 6 is burned by the heat of the molten metal,and a casting 'similar in shape to the main body 7 of the form 6 can beproduced.

The interior of the flask is maintained at a subatmospheric pressurewhile the molding operation is being performed, so that the integrity ofthe tiller material 12 is maintained without undergoing disintegration.

The openings 8 and 9 in the form 6 may be formed by using separatecores.

A second embodiment of the invention will be described with reference toFIG. 2 in which 21 is a flask having an open top and having anevacuation chamber 22 formed therein by partitioning a central portionof the flask 21 from the evacuation chamber .22 by a porous partition23. A filter 25 which may be made of wire netting is mounted on theinner side of the porous partition 23 such that the filter closes smallopenings 24 in the porous partition 23. Evacuation ports 26 which aremaintained in communication with the evacuation chamber 22 are providedin the flask 21 and connected to a vacuum pump (not shown) or othersuction means.

27 designates a form made of an instantaneously combustible material.The form 27 is made of a foamed synthetic resinous material or othermaterial which is readily burned by the heat of a molten metal when thelatter is poured and formed into a shape which is similar to the shapeof a product to be produced by casting.

A runner 28 made of an instantaneously combustible material is formedintegrally with the pattern 27 at one side thereof, and a gate 29 madeof an instantaneously combustible material is formed integrally with therunner 28 at its upper portion. The gate 29 diverges upwardly.

filler material, production of inclusions and occurrence of fusion.

A third embodiment of the invention will be described with reference toFIG. 3. A- form 27 shown thereinis similar to that shown in FIG. 2except for the fact that the former is formed integrally at the otherside thereof with a gas vent 33, and a gas passage 34 extending throughthe gas vent 33 into the interior of the form 27. A shield member 30covers outer surfaces of the form 27 as well as the runner28, gate 29and gas vent 33.

The form 27 as well as the runner 28, gate 29 and gas vent 33 isembedded in a filler material 31 filled in a flask 21 in the same manneras described with reference to the second embodiment. A lid 32 is placedon 1 the upper surface of the flask 21 with an upper end of A shieldmember 30 covers outer surfaces of the runner 28 and gate 29, or byforming a layer of plaster or clay on the outer surfaces of the form,runner 28 and gate 29.

A filler material 31 which may be molding sand or other heat resistingparticle material containing no binder therein is filled in the centralportion of the flask 21 partitioned from the evacuation chamber 22 bythe porous partition 23 to a suitable depth, and the form 27 integrallyformed with the runner 28 and gate 29 is place on the filler material 31in the central portion of the flask 21.

Then, the tiller material 31 is again filled in the central portion ofthe flask 21 to embed the form 27, runner 28 and gate 29 in the fillermaterial 31'. Thereafter,

5 a lid 32 which may be of a synthetic resin film is placed on the opentop of the flask 21.

If the suction means connected to the evacuation ports 26 provided inthe flask 21 is actuated, then the interior of the central portion ofthe flask 21 is evacuated through the evacuation chamber 22. Thus, anegative orsubatmospheric pressure is induced in the central portion ofthe flask 21 and relative'movements of the particles of the fillermaterial are precluded and the filler material 31 is rendered compactand formed in the shape of the shaping surfaces of the form 27, runner28 and gate 29 along the outer surfaces thereof.

If a molten metal is poured into the gate 29 while the filler material31 in the flask 21 is maintained at a subatmospheric pressure, then themolten metal flows into the form 27 while burning the gate 29 and runner28 by its heat, and the form 27 itself is burned by its heat too. Atthis time, the shield member is attracted to the filler material becausethe tiller material is maintained at a sub-atmospheric pressure,although the inner surface of the shield member may be carbonized by theheat of the molten metal. In this way, the shield member 30 providescover to the surface of the tiller material and helps such surface to berendered compact and maintained in the same shape as the surface of theform 27, thereby preventing disintegration of the the gas vent 33extending outwardly through the lid.

The interior of the flask 21 is evacuated to induce a sub-atmosphericpressure therein so as to render compact and form the tiller material inthe shape of the form 27, runner 28, gate 29 and gas vent 33 along outersurfaces thereof.

If a molten metal is poured in the gate 29, then the molten metal flowsinto the form 27 while burning the gate 29 and runner 28 by its heat,and the form 27 itself is burned by its heat too. At this time, gasesproduced by the burning form 27 are vented to atmosphere through the gaspassage 34 in the gas vent 33 without staying in the form.

In the embodiment shown and described above, the gas vent 33 has beendescribed as being formed integrally with the form 27. It should beunderstood, however, that the gas vent need not be made of a combustiblematerial, and that the gas vent may be made of a material different fromthe material used for making the form and formed independently of theform to be placed on top of the form.

Other embodiments will be described with reference to FIG. 4, FIG. 5 andFIG. 6.

In FIG. 4 and FIG. 5, 41 designates a rectangular flask having open topand bottom and formed in its walls with a plurality of openings 42 forpermitting air to pass therethrough. A filter 43 made as of wire nettingis provided on the inner side of each wall of the flask 41 to close theopenings 42.

A ventilatory frame 45 having a communication passage 44 maintained incommunication with the openings 42 is provided around the outer surfacesof the walls of the flask 41, and support projections 46 and 47 projectoutwardly from the middle of the opposite end walls of the ventilatoryframe 45, one 47 of said support projections 46 and 47 being formedtherein with a communication port 48 connected to the communicationpassage 44.

In FIG. 5, 49 is one of a pattern members made of wood and in two pieceswhich is formed on one surface thereof with a shaping surface 50 whichis formed at one end thereof with ribs 51 for forming weirs and a rib 52for forming a runner contiguous with the ribs 51. An air passage 53 isformed in the pattern member 49, and a plurality of air ducts 54 areformed in the pattern member 49 to maintain communication between theair passage 53 and the shaping surface 50. A communication opening 55 isformed in the pattern member 49 to connect one end of the air passage 53to atmosphere.

In performing a molding operation, a shield member 56 which is 20 to 50microns in thickness and formed of a synthetic resin film is broughtinto intimate contact with the shaping surface 50 of the pattern member49 by heating or using a solvent while air on the shaping surface 50side is withdrawn from the communication opening 55 through the airpassage 53 and air ducts 54, so that the shield member 56 is formed intoa shape similar to the shape of the shaping surface 50 and ribs 51, 52.

A runner forming member 57 for the gate made of an instantaneouslycombustible synthetic resinous material is mounted on the rib 52, and agas vent forming member 58 also made of an instantaneously combustiblesynthetic resinous material is provided at the other end of the shapingsurface.

A flask 41 is brought into engagement with the shaping surface 50 of thepattern member 49 through the shield member 56 being disposedtherebetween, and a filler material 59, such for example as molding sandor other heat resisting particle material, is filled in the flask 41from above. Then, the flask 41 and pattern member 49 are caused tovibrate as a unit by a vibrator (not shown) so as to compactly pack thefiller material.

The upper surface of the flask 41 is covered with a lid 60 which may beformed of a synthetic resin film.

The interior of the flask 41 is evacuated by suction means connected tothe communication port 48 in the support projection 47 through thecommunication passage 44 formed in the ventilatory frame 45. and theplurality of openings 42 provided in the flask 41, so that a negative orsub-atmospheric pressure is induced in the flask 41 to draw the shieldmember 56 and lid 60 to the filler material 59 and preclude relativemovements of the particles of the filler material. Thus, a shield isformed by the shield member 56 between the shaping surface of thepattern member 49 and the filler material 59.

The interior of the flask 41 may be evacuated through a plurality ofevacuation lines each formed therein with a multitude of openings andhaving a filter wound therearound and arranged in side by siderelationship in the flask.

After a sub-atmospheric pressure is induced in the flask 41, the suctionmeans is disconnected, and the pattern member 49 is separated from theflask 41 while each other with a core 61 being interposed therebetween,so as to form a cavity 62 of the shape of the casting to be producedbetween the shield members 56, 56 and the core 61.

In pouring a molten metal, the molten metal is directly poured in a gate63 formed by the runner forming member 57 made of an instantaneouslycombustible synthetic resinous material to burn part of the shieldmembers, so that the molten metal begins to fill the cavity 62 through arunner 64 and weirs 65 formed in the shield members. The runner formingmember 57 is burned by the heat of the molten metal, but an openingsimilar in shape to the member 57 is formed in the filler material 59because a negative pressure is present in the interior of the flasks 41,41.

As the molten metal successively fills the cavity 62, I

gases in the cavity 62 are forced to move to the uppermost portion ofthe cavity, so that the gas vent forming member 58 is burned by the heatof the gases. However, an opening similar in shape to the gas ventforming member 58 if formed in the filler material in the same manner asdescribed with reference to the gate 63, thereby permitting the gases inthe cavity 62 to be vented out of the cavity into the flasks.

The instantaneously combustible synthetic resinous material used forforming the runner forming member 57 for the gate and the gas ventforming member 58 may be selected from bubble producing syntheticresins, such for example as polystyrene and polyethylene.

By pouring the molten metal through the runner formed of aninstantaneously combustible synthetic resinous material, the need toprovide a runner in the filler material when molding is effected iseliminated. Molding is facilitated by using the runner forming membermade of an instantaneously combustible synthetic resinous material forforming a runner in the filler material according to this invention.

What is claimed is:

l. A molding method, comprising: embedding both a form made of aninstantaneously combustible material, and a gas vent for venting gasesformed from combustion of said material, in a mass of heat resistantparticulate material contained in a flask; covering the open top of theflask with a plastic film as a lid; inducing a negative orsub-atmospheric pressure in said mass thereby compacting said mass whilemaintaining the shape of said form; and pouring a molten metal into theform while still inducing said negative or sub-atmospheric pressure themolten metal gassifying said combustible material; and removingresultant gases through said vent.

2. A molding method as set forth in claim 1 further comprising the stepof covering said form made of an instantaneously combustible materialwith a shield member.

3. A molding method as set forth in claim 2 further comprising the stepof providing a runner forming member made of an instantaneouslycombustible material in said shield member.

4. A molding method as set forth in claim 1 wherein said gas vent isformed of an instantaneously combustible material.

1. A molding method, comprising: embedding both a form made of aninstantaneously combustible material, and a gas vent for venting gasesformed from combustion of said material, in a mass of heat resistantparticulate material contained in a flask; covering the open top of theflask with a plastic film as a lid; inducing a negative orsub-atmospheric pressure in said mAss thereby compacting said mass whilemaintaining the shape of said form; and pouring a molten metal into theform while still inducing said negative or sub-atmospheric pressure themolten metal gassifying said combustible material; and removingresultant gases through said vent.
 2. A molding method as set forth inclaim 1 further comprising the step of covering said form made of aninstantaneously combustible material with a shield member.
 3. A moldingmethod as set forth in claim 2 further comprising the step of providinga runner forming member made of an instantaneously combustible materialin said shield member.
 4. A molding method as set forth in claim 1wherein said gas vent is formed of an instantaneously combustiblematerial.